We propose and study a new type of double-layer holey structure with a wide bandgap. The structure can have glide symmetry in two orthogonal directions but not 2-D glide symmetry. We report results in terms of dispersion diagrams calculated with the eigensolver of a commercial solver, as well as with a multimode transfer matrix approach that permits an accurate calculation of the attenuation constant. The results demonstrate that the bandgap of the proposed structure can provide a wider fractional bandwidth and a larger attenuation constant than those of a 2-D glide-symmetric holey configuration. Therefore, this new type of periodic structure can be advantageous in preventing leakage in gap waveguide technology or, in general, parallel plate configurations and filters. The operation of this new unit cell is experimentally demonstrated with a double-flange configuration between 40-60 GHz.

Recently, digital and programmable metasurface has evolved into a new branch as information metasurface owing to its real-time manipulation of electromagnetic (EM) waves and simultaneous modulation of digital signals. Here, we present the theoretical model of information metasurface and analyze its capability of wave manipulation and signal modulation. Further, we extend the single-metasurface model into a multi-metasurface one, and discuss the feasibility and application of their joint operation. Our simulation results show its performance in high-precision harmonic scattering patterns, higher-order signal modulation, and spatial localization, demonstrating the potential of information metasurface in wireless communications and radar signal processing.

This paper evaluates the suitability of additive manufacturing, with AlSi10Mg using the Laser Powder-Bed Fusion (LPBF) technique, for geodesic lens antennas. This evaluation is carried out with three different geodesic lens antennas operating in Ka- V- and G-band. In the Ka-band, an elliptically-compressed geodesic lens antenna was designed, manufactured and tested; in the V-band, the experimental results of a geodesic lens array antenna composed of four elements are shown. These two designs were manufactured monolithically to avoid leakage and misalignment between the plates. Finally, the challenges of additive manufacturing at G-band are discussed. A dual-polarized geodesic Luneburg lens antenna working at 122.5 GHz has been produced in three parts, so polishing can be carried out to reduce the surface roughness. The overall results corroborate that additive manufacturing with the LPBF technique is a promising method to produce metal-only solutions for geodesic lens antennas in the millimetre-wave regime.

A double-layer lens consists of a pair of rotationally symmetric index profiles or geodesic lens shapes connected by a reflecting mirror partially covering their common periphery. Such a lens can provide a focus in each layer, and a wave travelling between the foci explores both layers. Here, we concentrate on the case with one layer being homogeneous or flat, and derive a general solution for the lens profiles by solving a Luneburg-like inverse problem with pre-specified foci inside or outside the lens, and different background indices in two layers. We demonstrate four examples of interest in ray-tracing plots. These lenses may find application in communications, sensing, and imaging from millimeter waves up to the optical bands.

We present a dual-polarized lens antenna for point-to-multipoint communications at sub-THz. The lens is constructed by a doubly-curved parallel plate following a geodesic lens shape equivalent to the Luneburg index profile. The polarization is changed by metallic screens patterned with complementary split resonant rings (CSRRs). These screens are integrated in the radiation aperture of the lens. Two lenses are stacked up, one for each polarization. Each lens is fed by 11 waveguide ports, providing beam steering or multiple beams. The antenna is fully metallic and hence, highly efficient. In the operating band from 115 GHz to 125 GHz, the simulation shows a realized gain of 20 dBi with a maximum scan loss of 0.6 dB up to 60 degrees, a cross-polarization discrimination around 20 dB, and an insertion loss smaller than 1.5 dB.

We propose and implement a geodesic half-Maxwell fish-eye (MFE)-lens antenna. The lens was optimized using an in-house physical optics (PO) code adapted for generalized geodesic lenses. The final antenna design was validated with commercial electromagnetic simulation software. The antenna combines a modulated geodesic half-MFE lens and a transition to a linear flare, which is needed to preserve the linear polarization in the aperture. The antenna prototype, designed to operate in the K-a-band, was manufactured with computer numerical control (CNC) milling and measured in an anechoic chamber. The design provides continuous beam scanning because of a mechanically actuated feed. Promising beam scanning properties are demonstrated in an angular range of +/- 45 degrees with a scan loss below 3 dB, as well as good frequency stability from 26 to 32 GHz. Since the antenna is fully metallic, its radiation efficiency is high (approximately 90%).

The linearized Multimodal Transfer-Matrix Approach (MMTMA) is a systematic hybrid solution to efficiently compute the dispersion analysis of two-/three-dimensional (2-/3-D) general periodic structures. This approach linearizes the nonlinear eigenvalue problem associated with 2-D/3-D periodic structures, avoiding the search for complex wavenumber solutions (both the phase and/or attenuation constants) in the complex plane. Here, MMTMA is explained and used for the Bloch analysis of a 2-D periodic leaky-wave antenna.

We propose a pillbox antenna in combination with a geodesic lens at 60 GHz. The antenna is implemented in a dual-layer parallel plate waveguide. The waves from a geodesic lens in a first layer, after being reflected by a parabolic mirror connecting the rims of the two layers, enter a second layer and illuminate the radiation aperture. Since the lens produces a virtual focus, the reflector works as if it is fed from that a further location, making the system more compact.

A double-layer lens consists of a first gradient-index/geodesic profile in an upper waveguide, partially surrounded by a mirror that reflects the wave into a lower guide where there is a second profile. Here, we derive a new family of rotational-symmetric inhomogeneous index profiles and equivalent geodesic lens shapes by solving an inverse problem of pre-specified focal points. We find an equivalence where single-layer lenses have a different functionality as double-layer lenses with the same profiles. As an example, we propose, manufacture, and experimentally validate a practical implementation of a geodesic double-layer lens that is engineered for a low-profile antenna with a compact footprint in the millimeter wave band. Its unique double-layer configuration allows for two-dimensional beam scanning using the same footprint as an extension of the presented design. These lenses may find applications in future wireless communication systems and sensing instruments in microwave, sub-terahertz, and optical domains. A double-layer lens consists of a first gradient-index/geodesic profile in an upper waveguide, partially surrounded by a mirror that reflects the wave into a lower guide where there is a second profile. A family of such lens profiles are derived.

A systematic and efficient multimodal transfer-matrix approach is proposed for the comprehensive Bloch analysis of general 1-D/2-D/3-D periodic structures. We provide a linearization procedure for transforming the original nonlinear eigenvalue problem associated with 2-D/3-D structures to a standard one that can easily be solved without the need of a zero-searching algorithm in the complex plane. The proposed approach has been validated with bounded/open structures with complex geometries and/or inhomogeneous lossless/lossy materials. It demonstrates a significantly reduced computational time and leverages the strengths of full-wave simulators to deal with general problems and ad hoc quasi-analytical methods to give a fundamental understanding of the behavior of the structure. Also, it allows for an accurate evaluation of the imaginary part of the wavenumber, which offers information of material dissipation, stopband rejection, leakage, and complex modes.